Device for determining the fluid level in a container and container having such a device

Abstract

In a device for detecting filling level of liquid in a container, a protective tube (6) extends over a membrane (5) which can be placed in vibration by an electromechanical transducer (4). In this way, bubbles which rise in the liquid cannot reach the membrane and induce a false measurement of low filling level.

We claim: 
     
       1. A device for detecting a filling level of fluid in a container, comprising a membrane;   means for holding said membrane within said container with one side of said membrane facing the fluid to be measured;   an electromechanical transducer disposed within said holding means contiguous the side of the membrane opposite said one side for placing the membrane in vibration, which vibration is damped by contact of the membrane with the fluid; and wherein   said holding means includes a protective tube encircling said membrane and extending beyond the membrane towards the fluid to be measured.   
     
     
       2. The device according to claim 1, wherein the protective tube has on its inner side a run-off bevel which extends with a slope to an outer end of said tube. 
     
     
       3. The device according to claim 2, wherein said protective tube is provided on its inner side with a conical widening which widens in a direction away from said membrane.   
     
     
       4. The device according to claim 1 wherein, said protective tube has at least one opening at its uppermost point in its installed position.   
     
     
       5. The device according to claim 1 wherein the protective tube is formed as a half-shell which, in its installed position, is open at the top and towards the front of said device.   
     
     
       6. A unitary construction of a container and fluid-level measuring device for a fluid contained in the container, wherein the container comprises a side wall and a tube extending from said side wall inwardly of the container; and wherein said device is supported within an extension of said tube and comprises   a membrane with one side facing the fluid to be measured; and   an electromechanical transducer disposed on the opposite side of the membrane for placing the membrane in vibration, which vibration is damped by contact of the membrane with the fluid; and wherein   said tube extends beyond the membrane of the device, thereby forming a protective tube for the membrane.   
     
     
       7. A construction according to claim 6, wherein said transducer is a piezoelectric element in contact with said membrane.   
     
     
       8. A device for detecting a filling level of fluid in a container, comprising: a membrane with one side facing the fluid to be measured;   an electromechanical transducer disposed on the opposite side of the membrane for placing the membrane in vibration;   the plane of said membrane is disposed in vertical direction; and   a protective tube in which said membrane is disposed extends beyond the membrane towards the fluid to be measured.